In order to facilitate the on-line detection of electromagnetic flowmeters, we suggest that a standard measuring pipe section can be configured during system design for new pipelines to facilitate the on-line inspection of electromagnetic flowmeters. The installation of the standard measuring pipe section shall be based on the requirements of the ultrasonic flowmeters for the forward and backward straight pipe sections. Care shall be taken to ensure that the liquid fills the measuring pipe. At the same time, the pipeline parameters, the material of the pipeline, the outer diameter of the pipe, the wall thickness of the pipe, the material and the thickness of the inner lining of the pipe are recorded. For the existing old pipeline, a measuring point that satisfies the conditions of use of the ultrasonic flowmeter can be selected on the pipeline to be measured, a piece of stainless steel pipe is installed, and the parameters of the stainless steel pipe are recorded at the same time. How to ensure the accuracy of on-line testing We believe that the following points can be taken into account to ensure the accuracy of the on-line detection of electromagnetic flowmeters: 1. Prepare for online testing . Iron Round Rod,Grinding Rod,Stainless Steel Round Bar,Cold Drawn Steel Round Bar Wuxi Sixleaf Machinery Co. LTD , https://www.sixleafmachine.com
Using the ultrasonic flowmeter certified by the statutory body as a standard table for online comparison to determine the measurement accuracy of the measured electromagnetic flowmeter. For sewage electromagnetic flowmeters, it is generally possible to select when the amount of suspended solids is small, and to keep the liquid temperature stable. When the conditions permit, clean water calibration can be used to improve the measurement accuracy of the ultrasonic flowmeter.
The accuracy of the ultrasonic flow meter to measure the fluid flow is closely related to the user's understanding of the on-site operating conditions. Before the inspector starts testing, he should first determine the following information:
1 . 1. When selecting the probe installation location, the following conditions should be met:
(1) There is not much dust and corrosive gas in the workplace;
(2) straight pipe length: 10D over the upstream side, downstream side l5D above (when the flow rate is low, may be appropriate to reduce the straight pipe requirements);
(3) There must be no disturbance factors ( such as pumps, valves, etc. ) within 30D on the upstream side ;
(4) The fluid must be filled with pipes and must not contain bubbles or excessive impurities;
(5) The pipeline where the probe is installed should not have strong mechanical vibration;
(6) There is ample space around the pipe where the probe is installed.
1 . 2. The exact values ​​of the material of the pipeline to be inspected, the outer diameter of the pipe, the wall thickness of the pipe, the material and thickness of the inner lining of the pipe, the medium in the pipe, the temperature of the medium, etc., are required to be measured and verified at the inspection site to ensure the measurement accuracy.
1 . 3. Common traffic points for on-site operating conditions to detect common user traffic points and improve the accuracy of online detection.
1 . 4. The basic principle of online flow detection using ultrasonic flowmeters is the standard table comparison method. Therefore, ultrasonic flowmeters should be regularly verified by the national statutory metrological verification agencies and obtain valid verification certificates.
2 , online detection work
This is a work that is technically and empirically demanding. Therefore, it is necessary to conduct rigorous training for the testing personnel. In particular, it requires the staff to conduct online inspections in a scientific manner. In actual use, we found that most of the measurements were inaccurate due to improper installation of the probe. Therefore, the correct installation of the probe becomes the first problem. We believe that the following are the principles that should be followed during probe installation.
(1) For horizontal piping, the probe should be installed within ±45° of the horizontal centerline ;
(2) The probe should be avoided from being installed in the deformed part, flange or welded part of the pipeline;
(3) Before installation, handle the probe mounting surface. First remove the rust, dirt, etc. on the surface of the pipe. (When the surface of the pipe has a protective layer, the protective layer should be stripped first ) to make the surface of the pipe surface smooth and free of dirt. Cleaning range should reach the entire circumference of the probe installation distance L + 200mm width;
(4) Apply the couplant to the entire emitting surface of the probe without forming bubbles;
(5) Apply silicone grease to the surface of the pipeline;
(6) Stick the probe firmly on the pipe wall and fix the probe with steel strap ( Note: The direction of the two probes must be opposite ) .
Input the flowmeter that has been verified by the on-site measurement into the flowmeter and check the signal reception. After confirming that the work is normal, the test can be started. During the test, different flow points are determined according to the commonly used flow rate, which can be adjusted by a water pump or a valve, and the flow rate indications of the standard flow meter and the detected flow meter are simultaneously collected to determine the indication error of the detected flow meter. When reading the flow rate display value, it should be performed when the flow rate is stable, and read the 10 or so display values in the same period of time to take the average value to reduce the error caused by the reading.